Pulverized-coal supply system for coal gasification furnace

ABSTRACT

To provide a pulverized-coal supply system for a coal gasification furnace in which the consumption of inert gas (the amount used) can be reduced. The pulverized-coal supply system is equipped with a pulverized-coal supply hopper ( 3 ) that receives pulverized coal pulverized by a coal pulverizer ( 1 ); a first pressure tank ( 31 ) that, when the pulverized-coal supply hopper ( 3 ) receives the pulverized coal, temporarily recovers part of inert gas filled in the pulverized-coal supply hopper ( 3 ) and supplies the recovered inert gas into the pulverized-coal supply hopper ( 3 ), whose interior is in an atmospheric pressure state; and a second pressure tank ( 32 ) filled with inert gas having a pressure necessary for increasing the inner pressure of the pulverized-coal supply hopper ( 3 ) to a predetermined pressure.

TECHNICAL FIELD

The present invention relates to a pulverized-coal supply system for a coal gasification furnace.

BACKGROUND ART

A known example of a pulverized-coal supply system for a coal gasification furnace is disclosed in PTL (Patent Literature) 1.

CITATION LIST Patent Literature

-   {PTL 1} Japanese Unexamined Patent Application, Publication No.     2000-119666

SUMMARY OF INVENTION Technical Problem

The pulverized-coal supply system for a coal gasification furnace disclosed in PTL 1, described above, adopts a second-stage pressurization method shown in FIG. 5 to make the pressure in a supply hopper in an atmospheric pressure state higher than the pressure in a gasification furnace in the shortest possible time when refilling (replenishing) the supply hopper with pulverized coal (fuel).

However, in the second-stage pressurization method shown in FIG. 5, all of inert gas (for example, N₂) filled in the supply hopper is released (discharged) into the atmosphere when the pressure in the supply hopper is brought to the atmospheric pressure state to receive the next load of pulverized coal after the supply of pulverized coal stored in the supply hopper is finished. This therefore has the problem of increasing the consumption of inert gas (the amount used), thus being uneconomical.

The present invention is made in consideration of such circumstances, and an object thereof is to provide a pulverized-coal supply system for a coal gasification furnace in which the consumption of inert gas (the amount used) can be reduced.

Solution to Problem

To solve the above problem, the present invention adopts the following solutions.

A pulverized-coal supply system for a coal gasification furnace according to a first aspect of the present invention comprises a pulverized-coal supply hopper that receives pulverized coal pulverized by a coal pulverizer; a first pressure tank that, when the pulverized-coal supply hopper receives the pulverized coal, temporarily recovers part of inert gas filled in the pulverized-coal supply hopper and supplies the recovered inert gas into the pulverized-coal supply hopper, whose interior is in an atmospheric pressure state; and a second pressure tank filled with inert gas having a pressure necessary for further increasing the inner pressure of the pulverized-coal supply hopper to a predetermined pressure to supply the pulverized coal to the gasification furnace.

With the pulverized-coal supply system for a coal gasification furnace according to the first aspect described above, when the pulverized-coal supply hopper receives pulverized coal, part of the inert gas filled in the pulverized-coal supply hopper is temporarily recovered into the first pressure tank, and the recovered inert gas is again filled into the pulverized-coal supply hopper in an atmospheric pressure state.

This allows the consumption of inert gas (the amount used) to be reduced.

In the pulverized-coal supply system for a coal gasification furnace described above, more preferably, at least two of the pulverized-coal supply hoppers are provided, wherein when at least one of the pulverized-coal supply hoppers receives the pulverized coal, the other pulverized-coal supply hopper supplies the pulverized coal to the gasification furnace.

Such a pulverized-coal supply system for a coal gasification furnace allows the gasification furnace to be supplied with pulverized coal continuously and stably.

In the pulverized-coal supply system for a coal gasification furnace described above, more preferably, the capacity of the first pressure tank is from 25% to 100% of the capacity of the pulverized-coal supply hopper.

Such a pulverized-coal supply system for a coal gasification furnace allows the capacity of the first pressure tank to be equal to or smaller than the capacity of a first-stage pressure tank used in the conventional second-stage pressurization method, thus reducing the size of the entire pulverized-coal supply system for a coal gasification furnace.

An integrated coal gasification combined cycle facility according to a second aspect of the present invention is equipped with any one of the above pulverized-coal supply systems for a coal gasification furnace.

Since the integrated coal gasification combined cycle facility according to the second aspect described above is equipped with the pulverized-coal supply system for a coal gasification furnace in which the consumption of inert gas (the amount used) can be reduced, running costs can be reduced in the case where a facility for producing inert gas (for example, the air separation unit denoted by reference sign 11 in FIG. 1) is not provided, so that inert gas must be purchased from another place.

Furthermore, in the case where a facility for producing inert gas (for example, the air separation unit denoted by reference sign 11 in FIG. 1) is provided, the facility can be made compact, so that the initial investment can be reduced, and power for the facility can also be reduced, allowing running costs to be reduced.

A method for operating a pulverized-coal supply system for a coal gasification furnace according to a third aspect of the present invention is a method for operating a pulverized-coal supply system for a coal gasification furnace comprising a pulverized-coal supply hopper that receives pulverized coal pulverized by a coal pulverizer; a first pressure tank that, when the pulverized-coal supply hopper receives the pulverized coal, temporarily recovers part of inert gas filled in the pulverized-coal supply hopper; and a second pressure tank filled with inert gas having a pressure necessary for increasing the inner pressure of the pulverized-coal supply hopper to a predetermined pressure, wherein the inert gas recovered into the first pressure tank is filled into the pulverized-coal supply hopper, whose interior is in an atmospheric pressure state, and thereafter, the inert gas filled in the second tank is filled into the pulverized-coal supply hopper.

With the method for operating the pulverized-coal supply system for a coal gasification furnace according to the third aspect described above, when the pulverized-coal supply hopper receives pulverized coal, part of the inert gas filled in the pulverized-coal supply hopper is temporarily recovered into the first pressure tank, and the recovered inert gas is again filled into the pulverized-coal supply hopper.

This allows the consumption of inert gas (the amount used) to be reduced.

In the method for operating the pulverized-coal supply system for a coal gasification furnace described above, more preferably, at least two of the pulverized-coal supply hoppers are provided, wherein when at least one of the pulverized-coal supply hoppers receives the pulverized coal, the other pulverized-coal supply hopper supplies the pulverized coal to the gasification furnace.

Such a method for operating the pulverized-coal supply system for a coal gasification furnace allows the gasification furnace to be supplied with pulverized coal continuously and stably.

Advantageous Effects of Invention

The pulverized-coal supply system for a coal gasification furnace according to the present invention provides the advantage of reducing the consumption of inert gas (the amount used).

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a configuration diagram showing, in outline, the configuration of an integrated coal gasification combined cycle facility equipped with a pulverized-coal supply system for a coal gasification furnace according to an embodiment of the present invention.

FIG. 2 is a configuration diagram showing, in outline, the configuration of a pulverized-coal supply system for a coal gasification furnace according to an embodiment of the present invention.

FIG. 3 is a graph for explaining the process of refilling (replenishing) a pulverized-coal supply hopper of a pulverized-coal supply system for a coal gasification furnace according to an embodiment of the present invention with pulverized coal (fuel).

FIG. 4 is a graph showing the relationship between the capacity of a depressurization recovery tank relative to the capacity of a pulverized-coal supply hopper and the amount of inert gas that can be recovered by the depressurization recovery tank.

FIG. 5 is a graph for explaining a second-stage pressurization method in a conventional pulverized-coal supply system for a coal gasification furnace.

DESCRIPTION OF EMBODIMENT

Referring to FIGS. 1 to 4, a pulverized-coal supply system for a coal gasification furnace (a pulverized-coal supply unit for a coal gasification furnace) according to an embodiment of the present invention will be described hereinbelow.

An integrated coal gasification combined cycle facility 50 of an embodiment shown in FIG. 1 adopts an air combustion system in which coal gas is generated in a gasification furnace 4 by using air as an oxidizing agent and supplies the coal gas, after being purified in a gas purification unit 7, to a gas turbine 8 as fuel gas. In other words, the integrated coal gasification combined cycle facility 50 shown in FIG. 1 is an air-combustion-type (air-blown) integrated coal gasification combined cycle facility (hereinafter referred to as “air-blown IGCC system”).

This air-blown IGCC system 50 introduces part of exhaust gas that has performed work in the gas turbine 8 and an exhaust-heat recovery boiler 9, to be described later, as drying gas and supplies coal used as a raw material to a coal pulverizer 1 together with this drying gas. The coal pulverizer 1 heats the supplied coal with the drying gas and pulverizes the coal into fine particles while removing water in the coal to produce pulverized coal.

The thus-produced pulverized coal is carried to a bag filter (cyclone) 2 by the drying gas. In the interior of the bag filter 2, the gas component, such as the drying gas, and the pulverized coal (particle component) are separated, and the gas component is exhausted from the bag filter 2. On the other hand, the pulverized coal of the particle component falls due to gravity and is recovered by a pulverized-coal supply hopper (hereinafter referred to as “hopper”) 3.

The pulverized coal recovered in the hopper 3 is carried into the gasification furnace 4 by nitrogen gas (carrier gas) introduced as a pressure carrier from an air separation unit 11, to be described later.

The gasification furnace 4 is supplied with pulverized coal and char, to be described later, as raw materials for coal gas. In the gasification furnace 4, coal gas that is gasified from the pulverized coal and char is produced using compressed air supplied from compressors 12 and 13 and oxygen supplied from the air separation unit 11 as oxidizing agents.

The coal gas gasified in the gasification furnace 4 in this way is introduced from the upper part of the gasification furnace 4 to a gas cooler 5, where it is cooled. This coal gas is cooled by the gas cooler 5 and is thereafter supplied to a char recovery unit 6.

In the char recovery unit 6, the char generated together with the coal gas gasified from the pulverized coal is separated. The coal gas flows out from the top of the char recovery unit 6 and is supplied to the gas turbine 8 through the gas purification unit 7.

The gas purification unit 7 purifies the coal gas to produce fuel gas for the gas turbine 8.

The fuel gas (coal gas) produced in this way is supplied to a combustor of the gas turbine 8, where it is burned to generate high-temperature, high-pressure exhaust combustion gas.

This exhaust combustion gas drives the turbine of the gas turbine 8 and is thereafter discharged as high-temperature exhaust gas. The thus-driven gas turbine 8 can drive a generator 14 to generate electricity because a main shaft that rotates together with the turbine is connected to the generator 14.

The high-temperature exhaust gas discharged from the gas turbine 8 is supplied to the exhaust-heat recovery boiler 9, where the high-temperature exhaust gas is used as a heat source for generating steam. The exhaust gas used to generate steam in the exhaust-heat recovery boiler 9 is subjected to necessary treatment by a denitration unit (not shown) or the like and is thereafter exhausted into the atmosphere.

Furthermore, part of the exhaust gas that is used to generate steam by the exhaust-heat recovery boiler 9 is extracted as drying gas for the coal pulverizer 1 and is supplied to the coal pulverizer 1 through a drying gas channel G1. For this drying gas, exhaust gas subjected to treatment, such as denitration, is used. Furthermore, the steam generated in the exhaust-heat recovery boiler 9 is supplied to a steam turbine 15 or the like for generating electricity.

The char recovered by the char recovery unit 6, described above, falls into a char supply hopper 10 due to gravity, where it is recovered. The char in the char supply hopper 10 is carried by nitrogen, which is supplied from the air separation unit 11, and is returned to the gasification furnace 4 by using the nitrogen as carrier gas. The char returned to the gasification furnace 4 is used together with the pulverized coal as a raw material for gasification.

In this way, by gasifying the pulverized coal obtained by pulverizing coal in the gasification furnace 4 using air and oxygen as oxidizing agents, coal gas and char are generated. The coal gas is used as fuel gas for the gas turbine 8, and the char separated from the coal gas is again supplied to the gasification furnace 4, where it is gasified.

In FIG. 1, reference sign 16 denotes a raw coal bunker, reference sign 17 denotes a bin, reference sign 18 denotes a cyclone that constitutes the char recovery unit 6, reference sign 19 denotes a porous filter that constitutes the char recovery unit 6 together with the cyclone 18, reference sign 20 denotes a char bin, reference sign 21 denotes an electric motor that rotationally drives the compressor 13, reference sign 22 denotes a chimney, reference sign 23 denotes a combustor, and reference sign 24 denotes a pulverized-coal dry blower.

A pulverized-coal supply system 30 for a coal gasification furnace according to this embodiment includes at least two (in this embodiment, two) hoppers 3 and at least one (in this embodiment, one) depressurization evacuation recovery tank (first pressure tank) 31, and at least one (in this embodiment, one) pressure tank (second pressure tank) 32.

A fuel supply pipe 35, an atmosphere release pipe 36, and a depressurization evacuation pipe 37 are connected to the top of each hopper 3.

One end (upstream end) of the fuel supply pipe 35 is connected to the bottom of the bin 17, and the other end (downstream end) of the fuel supply pipe 35 is connected to the top of the hopper 3 so that pulverized coal (fuel) is supplied to the hopper 3 via the fuel supply pipe 35.

One end (upstream end) of the atmosphere release pipe 36 is connected to the top of the hopper 3, the other end (downstream end) of the atmosphere release pipe 36 is open to the atmosphere, and an atmosphere release valve V1 is connected to an intermediate portion of each atmosphere release pipe 36.

One end (upstream end) of the depressurization evacuation pipe 37 is connected to the top of the hopper 3, the other end (downstream end) of the depressurization evacuation pipe 37 is connected to the upper part of the body of the depressurization evacuation recovery tank 31, and a depressurization evacuation valve V2 is connected to an intermediate portion of the depressurization evacuation pipe 37.

A first inert-gas supply pipe (pressure pipe) 41 is connected to the upper part of the body of each hopper 3, and a second inert-gas supply pipe (pressure pipe) 42 is connected to the lower part of the body of each hopper 3.

One end (upstream end) of the first inert-gas supply pipe 41 is connected to the lower part of the body of the depressurization recovery tank 31, the other end (downstream end) of the first inert-gas supply pipe 41 is connected to the upper part of the body of the hopper 3, and a first inert-gas supply valve (pressure valve) V3 is connected to an intermediate portion of the first inert-gas supply pipe 41.

One end (upstream end) of the second inert-gas supply pipe 42 is connected to the body of the pressure tank 32, the other end (downstream end) of the second inert-gas supply pipe 42 is connected to the lower part of the body of the hopper 3, and a second inert-gas supply valve (pressure valve) V4 is connected to an intermediate portion of the second inert-gas supply pipe 42.

Next, a process for refilling (replenishing) the hopper 3 with pulverized coal (fuel) will be described using FIG. 3.

First, the depressurization evacuation valve V2 connected to the hopper 3 that is required to be refilled with pulverized coal (hereinafter referred to as “the relevant hopper 3”) is opened, and the inert gas filled in the relevant hopper 3 at a predetermined pressure of about 5 MPa is filled into the depressurization recovery tank 31 under an inner pressure of about 1.8 MPa via the depressurization evacuation pipe 37 ((1) in FIG. 3).

When the pressure in the relevant hopper 3 and the pressure in the depressurization recovery tank 31 become equal (reach an equal pressure (about 3.3 MPa)), the depressurization evacuation valve V2 is fully closed, and the atmosphere release valve V1 connected to the relevant hopper 3 is opened to bring the pressure in the relevant hopper 3 into an atmospheric pressure state to receive the pulverized coal supplied from the bin 17 ((2) in FIG. 3).

After completion of the refilling of the pulverized coal into the relevant hopper 3, the atmosphere release valve V1 is fully closed, and the first inert-gas supply valve V3 connected to the relevant hopper 3 is opened to fill the inert gas having a pressure of about 3.3 MPa, which is filled (recovered) in the depressurization recovery tank 31 in advance, into the relevant hopper 3 ((3) in FIG. 3).

When the pressure in the relevant hopper 3 and the pressure in the depressurization recovery tank 31 become equal (reach an equal pressure (about 1.8 MPa)), the first inert-gas supply valve V3 is fully closed, the second inert-gas supply valve V4 connected to the relevant hopper 3 is opened to increase the pressure in the relevant hopper 3 to a predetermined pressure of about 5 MPa, and the process of refilling (replenishing) the hopper 3 with pulverized coal (fuel) is completed ((4) in FIG. 3).

As shown in FIG. 4, for example, in the case where the capacity of the hopper 3 and the capacity of the depressurization recovery tank 31 are set equal (at 100% on the horizontal axis in FIG. 4), about 38% of inert gas to be filled into the hopper 3 can be recovered by the depressurization recovery tank 31; in the case where the capacity of the depressurization recovery tank 31 is set to half of that of the hopper 3 (at 50% on the horizontal axis in FIG. 4), about 30% of inert gas to be filled into the hopper 3 can be recovered by the depressurization recovery tank 31; and in the case where the capacity of the depressurization recovery tank 31 is set to a quarter of that of the hopper 3 (at 25% on the horizontal axis in FIG. 4), about 20% of inert gas to be filled into the hopper 3 can be recovered by the depressurization recovery tank 31.

In addition, as shown in FIG. 4, even if the capacity of the depressurization recovery tank 31 is set larger than the capacity of the hopper 3 (even if the capacity ratio comes to the right of 100% on the horizontal axis in FIG. 4), there is little difference in the amount of inert gas that can be recovered by the depressurization recovery tank 31 and filled (refilled) into the hopper 3.

With the pulverized-coal supply system 30 for a coal gasification furnace according to this embodiment, when the hopper 3 receives pulverized coal, part of the inert gas filled in the hopper 3 is temporarily recovered into the depressurization recovery tank 31, and the recovered inert gas is again filled into the hopper 3.

This allows the consumption of inert gas (the amount used) to be reduced.

Furthermore, with the pulverized-coal supply system 30 for a coal gasification furnace according to this embodiment, two hoppers 3 are provided, and while one of the hoppers 3 is receiving pulverized coal, the other hopper 3 supplies pulverized coal to the gasification furnace 4.

This allows the gasification furnace 4 to be supplied with pulverized coal continuously and stably.

Furthermore, with the pulverized-coal supply system 30 for a coal gasification furnace according to this embodiment, the capacity of the depressurization recovery tank 31 is set from 25% to 100% of the capacity of the hopper 3.

This allows the capacity of the depressurization recovery tank 31 to be equal to or smaller than the capacity of a first-stage pressure tank used in the conventional second-stage pressurization method, thus reducing the size of the entire pulverized-coal supply system 30 for a coal gasification furnace.

Furthermore, since the integrated coal gasification combined cycle facility 50 according to the present invention is equipped with the pulverized-coal supply system 30 for a coal gasification furnace in which the consumption of inert gas (the amount used) can be reduced, running costs can be reduced in the case where a facility for producing inert gas (for example, the air separation unit denoted by reference sign 11 in FIG. 1) is not provided, so that inert gas must be purchased from another place.

Furthermore, in the case where a facility for producing inert gas (for example, the air separation unit denoted by reference sign 11 in FIG. 1) is provided, the facility can be made compact, so that the initial investment can be reduced, and power for the facility can also be reduced, allowing running costs to be reduced.

Furthermore, in the above embodiment, although a description is given of a case in which the integrated coal gasification combined cycle facility 50 is an air-blown IGCC system, it is not limited thereto; it may be, for example, an oxygen-blown IGCC system.

Note that the present invention is not limited to the above embodiment and that it can be modified or changed as appropriate.

REFERENCE SIGNS LIST

-   1 coal pulverizer -   3 (pulverized-coal supply) hopper -   4 gasification furnace -   30 pulverized-coal supply system for coal gasification furnace -   31 depressurization recovery tank (first pressure tank) -   32 pressure tank (second pressure tank) -   50 integrated coal gasification combined cycle facility 

1. A pulverized-coal supply system for a coal gasification furnace, the system comprising: a pulverized-coal supply hopper that receives pulverized coal pulverized by a coal pulverizer; a first pressure tank that, when the pulverized-coal supply hopper receives the pulverized coal, temporarily recovers part of inert gas filled in the pulverized-coal supply hopper and supplies the recovered inert gas into the pulverized-coal supply hopper, whose interior is in an atmospheric pressure state; and a second pressure tank filled with inert gas having a pressure necessary for increasing the inner pressure of the pulverized-coal supply hopper to a predetermined pressure.
 2. The pulverized-coal supply system for a coal gasification furnace according to claim 1, wherein at least two of the pulverized-coal supply hoppers are provided, and wherein when at least one of the pulverized-coal supply hoppers receives the pulverized coal, the other pulverized-coal supply hopper supplies the pulverized coal to the gasification furnace.
 3. The pulverized-coal supply system for a coal gasification furnace according to claim 1, wherein the capacity of the first pressure tank is from 25% to 100% of the capacity of the pulverized-coal supply hopper.
 4. An integrated coal gasification combined cycle facility comprising the pulverized-coal supply system for a coal gasification furnace according to claim
 1. 5. A method for operating a pulverized-coal supply system for a coal gasification furnace comprising: a pulverized-coal supply hopper that receives pulverized coal pulverized by a coal pulverizer; a first pressure tank that, when the pulverized-coal supply hopper receives the pulverized coal, temporarily recovers part of inert gas filled in the pulverized-coal supply hopper; and a second pressure tank filled with inert gas having a pressure necessary for increasing the inner pressure of the pulverized-coal supply hopper to a predetermined pressure, wherein the inert gas recovered into the first pressure tank is filled into the pulverized-coal supply hopper, whose interior is in an atmospheric pressure state, and thereafter, the inert gas filled in the second tank is filled into the pulverized-coal supply hopper.
 6. The method for operating the pulverized-coal supply system for a coal gasification furnace according to claim 5, wherein at least two of the pulverized-coal supply hoppers are provided, and wherein when at least one of the pulverized-coal supply hoppers receives the pulverized coal, the other pulverized-coal supply hopper supplies the pulverized coal to the gasification furnace. 